(a) Technical Field
The present disclosure generally relates to a combustion system for an engine. In particular, a dual pre-chamber combustion system is disclosed that facilitates the use of a lean air-fuel mixture.
(b) Background Art
One byproduct of internal combustion within an engine is the formation of nitrogen oxide (NOx) gasses. These types of gasses are formed when nitrogen (N2) combines with oxygen (O2) under the high temperatures associated with the combustion process, thereby forming NOx gasses such as nitric oxide (NO) and nitrogen dioxide (NO2). These gasses can have a number of adverse environmental effects when released into the atmosphere. For example, acid rain, smog, ozone layer depletion, and other adverse environmental effects have been attributed to the release of NOx gasses into the atmosphere.
One way to reduce NOx gas production in a combustion engine is by using a sufficiently lean air-fuel mixture. In particular, the increased amount of air in a lean air-fuel mixture has the effect of decreasing the internal combustion temperatures of the engine, thereby lowering the formation of NOx gasses. However, the use of a lean air-fuel mixture is not without challenges. For example, running an overly lean air-fuel mixture in a traditional combustion engine can cause engine damage and “knocking,” among other issues.
Some attempts have been made to support the use of lean and ultra-lean air-fuel mixtures in a combustion engine by making certain modifications to the engine. One such approach has been to use a stratified charge in a gasoline direct injection (GDI) engine. For example, a GDI wall guided design typically uses specialized contours on a piston to direct fuel injected from a side injector towards a centrally located spark plug. In other cases, indirect injection designs have been used in which a fuel injector and spark plug are both located within a pre-chamber, allowing combustion to begin in the pre-chamber and spread to the primary combustion chamber. However, such approaches require complex designs and may have only marginal effects on fuel economy.
In order to solve the problems in the related art, there is a demand for the development of a simplified combustion system that both reduces NOx gas emissions and improves fuel economy.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.